The present invention relates to wear resistant overlays and dxc3xa9cor sheets for use in decorative laminates and floorings and to laminates and flooring prepared therefrom. Decorative laminates have been conventionally made by stacking a plurality of layers of paper impregnated with synthetic thermosetting resins. Normally, the assembly consists of a plurality (for example, three to eight) core sheets made from phenolic resin impregnated Kraft paper, above which lies a decor sheet, usually a print or solid color, impregnated with melamine resin. An overlay sheet, known as a WROL, is often provided on top of the decor sheet which, in the laminate, is made to be as transparent and as wear-resistant as possible thereby allowing the decor sheet to be seen through the overlay while providing protection for the decor sheet from being damaged by scratches and scuffs.
Additionally, it has been found that different desired appearances can be created in the dxc3xa9cor sheet by the addition of various decorative particles or additives directly to the paper furnish prior to the deposition of the dxc3xa9cor sheet furnish on the paper web. The addition of these types of decorative particles directly to the paper furnish of the dxc3xa9cor sheet is generally well known in the industry. However, while the addition of the decorative particles directly to the paper furnish has been found to produce generally acceptable results while producing the desired visual effect for some particles, production of the paper in this manner can be somewhat wasteful because the decorative particles tend to be dispersed throughout the entire paper sheet when in fact only the decorative particles relatively close to the top of the dxc3xa9cor sheet surface can actually be seen in the finished laminate.
Furthermore, while it has been found that the use of two separate sheets, namely a WROL sheet and a dxc3xa9cor sheet, has produced acceptable wear resistant laminates for most uses, the cost and complexity of the finished laminate is higher than if a single sheet could be found that incorporated both the decorative aspects of the dxc3xa9cor sheet and the wear-resistant aspects of the WROL. And, as is discussed in greater detail below, while the industry has recognized the general desirability for producing a single sheet that performs the wear-resistant role of a WROL with the decorative role of a dxc3xa9cor sheet, no such sheet has been acceptably produced that accomplishes these goals as disclosed and claimed in the present invention.
In this regard, it is well known that the incorporation of decorative chips into paper sheets for incorporation into wear-resistant laminate materials for use in flooring, countertops and furniture is well known in the art. For example, U.S. Pat. No. 4,126,727 discloses a laminate flooring material having pearlescent chips or flakes incorporated therein over an alternating light and dark background pattern to achieve a desired decorative effect. In that patent, it is disclosed that the chips be blended into a synthetic, thermoplastic resinous polymer wear layer which is extruded or calendered to create a preformed sheet material. This sheet material is then laminated to other sheets to create the finished laminate product.
In another similar invention, U.S. Pat. No. 5,962,123 (assigned to the assignee of the present invention) discloses a laminate flooring material having decorative paper chips incorporated therein. In that patent, it is disclosed that the desired decorative effect may be achieved by adding the paper chips directly to the dxc3xa9cor sheet or overlay sheet furnish prior to the distribution of the furnish onto the web. The sheet produced thereby, whether it is an overlay or a dxc3xa9cor sheet, is then impregnated with a resin and laminated to additional sheets in order to form the finished laminate as is known in the industry. In yet another related invention, U.S. Pat. No. 5,202,180 discloses casting a plasticized vinyl web containing decorative metallic particles onto a reusable carrier web and then stripping off the vinyl web for incorporation into a suitable laminate.
Additionally, there have been prior art publications which have disclosed the desirability for eliminating the need for separate WROLs and dxc3xa9cor sheets and have proposed various methods for accomplishing that goal. For example, U.S. Pat. No. 4,255,480 discloses the addition of a thin layer of mineral particles (such as aluminum oxide) and microcrystalline cellulose directly to the top of a dxc3xa9cor sheet thereby obviating the need for a separate WROL.
Additional patents disclose other methods for producing the desired decorative effects in a dxc3xa9cor sheet. U.S. Pat. No. 4,271,221 to Hosmer discloses a coating composition that may be applied to a dxc3xa9cor sheet at the dry end. The coating composition can contain any desirable pigment, fillers (such as clay, calcium carbonate, talc, titanium dioxide, etc.) and a binder. The coating may be applied at the dry end using any well known coating apparatus including an air knife coater, blade coater, or roll coater. U.S. Pat. No. 5,034,084 to Schafer et al. discloses a dxc3xa9cor sheet for use in a decorative laminate. The disclosed dxc3xa9cor sheet includes two layers of a thermosetting resin coating wherein the first layer closest to the sheet xe2x80x9ccontains a flake or scale-shaped pigment in an amount of 2% to 40% by weightxe2x80x9d wherein the flake is preferably 5 to 100 microns in size and may be comprised of mica, metals, or metal alloys. The flake is mixed in with the coating resin prior to coating on the substrate that has been impregnated with an aminoplast resin.
However, until the present invention, none of the prior art paper structures have succeeded in fulfilling the need for a single low cost sheet for incorporation into a decorative laminate having the desired decorative and wear-resistant qualities as described above.
The present invention provides an alternative to prior art paper sheets for use in decorative laminates wherein decorative inclusions were generally added directly to the paper furnish and wherein separate decor sheets and WROLs were required to make the finished laminate. In contrast, the combined dxc3xa9cor/WROL sheet of the present invention provides the desired decorative effects and wear-resistant properties in a single sheet that can be made simply and inexpensively on existing papermaking equipment.
The dxc3xa9cor/WROL sheet of the present invention may be formed in a multitude of different ways. For example, in accordance with the invention, the decorative inclusion particles may be applied either at the wet end of the paper machine between the primary headbox and the couch roll or on the dry end using a size press or other known dry end coating equipment. The dxc3xa9cor/WROL sheet of the present invention includes decorative inclusion particles incorporated therein to give the sheet desired decorative effect. Examples of particles that have been found to provide the desired decorative effect include, but are not limited to: white, colored and interference pearlescent pigments (mica or other flat particles coated with metal oxides such as titanium dioxide or iron oxide); flat particles of thinly layered plastic that give interference colors; coated metal foil or metallized plastic particles in silver and various colors; natural and synthetic fibers in various colors; small paper or plastics chips, etc.
In accordance with the invention, the abrasive grit particles maybe added with the decorative inclusion particles or in other manners conventionally known in the industry. For example, after deposition oft he cellulose fibers on the papermachine wire from a first headbox, the wet web can then be overcoated with the grit particles, such as aluminum oxide, which are deposited from a secondary headbox located relatively closely thereto. In another method, the grit particles may be mixed in with the paper furnish at the primary headbox. In yet another method, the grit particles may be added by means of a curtain coater or a slot coater in a manner consistent with a preferred embodiment of the present invention is disclosed in U.S. Pat. No. 5,820,937, the contents of which are herein incorporated by reference.